Previous studies indicated that the blood of younger mice had similar effects on older members of the species.

Researchers have found that injecting older mice with the blood of teenage humans can help rejuvenate them, increasing both memory and physical ability. Previous studies showed similar results between young and old mice, but this was the first time that researchers introduced humans into the tests.

The revitalising effect seems to come from the blood's plasma, reported the New Scientist, citing that several studies suggested that injecting plasma from young mice into the organs of old ones had a similar rejuvenating effect.

To test the effect of teenage plasma, researchers took samples from 18 year olds and injected them twice-weekly into mice that were 12 months old – around the age that they typically start to show signs of ageing. After undergoing the injections for three weeks, the mice were tested against three-month-old mice and older ones that had not been injected with the blood.

Sakura Minami of research company Alkahest said the young human blood seemed to improve the cognition of the older mice: they were able to memorise mazes like younger mice and seemed physically fitter.

Not only did the mice do well in the tests, the researchers studied their brains and found that the injected mice had better neurogenesis – the process by which new brains cells are created. Victoria Bolotina, a professor at Boston University told the magazine that it was an expected result: "The blood of young people must have something in it that's important for keeping them young."

The company has been trialling the effects of young blood on people who suffer from Alzheimer's disease, and say they hope that the research could help people suffering with age-related issues in the future.